Idotea (Pentidotea) wosnessenskii (Brandt, 1851)
Common name(s): Rockweed isopod, Olive green isopod, Vosnesensky's isopod
|Synonyms: Pentidotea wosnessenskii, Idothea wosnessenskii|
|Idotea wosnessenskii from Padilla Bay.|
|(Photo by: Dave Cowles, July 2006)|
How to Distinguish from Similar Species: Of the species with a convex posterior margin to the pleotelson, several species look similar but pleonite 1 is not narrower laterally than in the center. Several others have a more slender body with all the pereonites about the same width. Idotea aculeata, in the southern part of the range, looks similar but has round eyes instead of kidney-shaped.
Geographical Range: Alaska to central CA; Sea of Okhotsk, USSR.
Depth Range: Mid intertidal to 16 m
Habitat: Often abundant in kelp, in mussel beds, and under intertidal rocks.
Biology/Natural History: Eats algae. May eat the egg capsules of Nucella emarginata. Predators include fish such as the spotted kelpfish Gibbonsia elegans and dwarf perch Micrometrus minimus. This species can swim well, using its pleopods (it opens the flaps of the uropods to expose the pleopods). Males are usually larger and paler than females and have thicker legs. Ovigerous females have been found in July, and a female was seen brooding 3-4 mm young in November in SE Alaska.
The species is named for the Russian zoologist Ilya Gavrilovich Vosnesensky, who collected and studied species from Siberia, Alaska, and California from 1839-1848
|Main Page||Alphabetic Index||Systematic Index||Glossary|
McConnaughey and McConnaughey, 1985
Morris et al., 1980
O'Clair and O'Clair, 1998
Ricketts et al., 1985
In this closeup of the head (cephalon) one can see the lateral eyes (kidney-shaped when viewed from the side) and the fact that the first pereonite is much wider than the cephalon.
In this view of the underside of the head one can see the palp along the side of the third maxilliped, which is covering the mouth (the dark mandibles are visible between the third maxillipeds).
The palp has 5 segments.
This view shows the last two pereonites (at top), then the two free pleonites and the front of the pleotelson.
The lateral plates seen on the pereonites are actually coxal plates. Note that the posterolateral margin of the coxal plate from the last (7th) pereonite is pointed (acute)
The first pleonite is narrow or acute at the edge, much narrower than it is mid-dorsally.
Note the notch at the sides of the front of the pleotelson showing the margin of a third partly free pleonite.
In this ventral view one can see the 7 similar pereopods on the pereon, and the flaplike ventral uropods which are characteristic of suborder Valvifera and cover the pleopods on the pleotelson.